Helen Slater had never been in a movie before she headlined Supergirl. It shouldn't have mattered. With blonde hair and bright blue eyes, Slater looked like Superman's cousin, Kara Zor-El, brought to life, and besides, nobody had ever heard of Christopher Reeve when Richard Donner cast him as Superman, and that worked out fine. What could go wrong?
A lot, as it turns out. Slater earned many accolades for her turn as the Girl of Steel—Roger Ebert said she had "the kind of freshness, good health, high spirits, and pluck that would be just right for the character" and called her "the best thing in the film"—but the rest of the movie never quite caught up. Supergirl's name stars, Peter O'Toole and Faye Dunaway, were savaged by reviewers, and the film's intentionally campy tone turned off all but the most diehard fans. In the aftermath, Supergirl's producers sold the rights to the entire Superman franchise, while DC Comics killed the Maid of Might in the comics after the movie failed.
Despite the positive reception to Slater's performance, she career never flew quite as high again—but she never left Supergirl behind, either. Decades later, Slater appeared on the television show Smallville, which told the story of a teenage Superman-in-training, as Lara, Kal-El's biological mother. On the CW's Supergirl, she later landed a recurring role as Eliza Danvers, Kara's adopted mother. She's also voiced Martha Kent, Superman's human mom, in the animated DC Super Hero Girls specials, and played a different DC Comics femme fatale, Talia al Ghul, in Batman: The Animated Series.